Various types of hydrogel sheet dressing are known and are available commercially. The properties of two such dressings are reported by S Thomas in J. Wound Care, 1993, 2, 176. Hydrogels have been recommended for use as wound contact layers. Desirably, a wound contact layer should be non-adherent, conformable and permeable to aqueous liquids such as wound exudate and should maintain its integrity during use.